Is it possible/worth it to fit a dump valve to a 1.9tdi?

No and nope! I believe such a device has no practical use on these engines.

Hello and Welcome to the forum

It is common for new members to ask about them, this is I normally say about dump valves for TDIs

The way that diesels work, a dump valve will not do anything at all if you fit one. This is because a diesel does not have a throttle valve and does not restrict the airflow into the engine when the throttle is closed, unlike a petrol one. There is a good explanation here: TDIClub FAQ - Blow-off valves or BOV or similar The rest of the FAQ is very useful as well.

You can fit an electronic operated dump valve, this will produce the sound of one but will not do anything to the performance of the car. I have even heard they actually decrease performance slightly when gear changing, and could damage the turbo, as it dumps more pressure than it needs to. This is what an electronic one will sound like:

Edited 11 June, 201115 yr by Jim H